struts2默认貌似只是支持VelocityLayoutServlet
那么如何使用VelocityLayoutServlet呢？
首先，要自己写点代码了，写个extends org.apache.struts2.dispatcher.VelocityResult 的类，取名曰：VelocityLayoutResult
实现如下：
package struts2.velocity;
import java.io.OutputStreamWriter;
import java.io.StringWriter;
import java.io.Writer;
import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.PageContext;
import org.apache.struts2.ServletActionContext;
import org.apache.struts2.dispatcher.VelocityResult;
import org.apache.struts2.views.JspSupportServlet;
import org.apache.struts2.views.velocity.VelocityManager;
import org.apache.velocity.Template;
import org.apache.velocity.context.Context;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
public class VelocityLayoutResult extends VelocityResult {
private static final long serialVersionUID = 6020934292083047099L;
private static final Logger LOG = LoggerFactory.getLogger(VelocityLayoutResult.class);
public static String KEY_SCREEN_CONTENT = "screen_content";
public static String KEY_LAYOUT = "layout";
public static final String PROPERTY_DEFAULT_LAYOUT = "tools.view.servlet.layout.default.template";
public static final String PROPERTY_LAYOUT_DIR = "tools.view.servlet.layout.directory";
public static final String PROPERTY_INPUT_ENCODING = "input.encoding";
public static final String PROPERTY_OUTPUT_ENCODING = "output.encoding";
public static final String PROPERTY_CONTENT_TYPE = "default.contentType";
protected VelocityManager velocityManager;
protected String defaultLayout;
protected String layoutDir;
protected String inputEncoding;
protected String outputEncoding;
protected String contentType;
@Override
public void setVelocityManager(VelocityManager mgr) {
this.velocityManager = mgr;
super.setVelocityManager(mgr);
}
@Override
public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
ValueStack stack = ActionContext.getContext().getValueStack();
HttpServletRequest request = ServletActionContext.getRequest();
HttpServletResponse response = ServletActionContext.getResponse();
JspFactory jspFactory = null;
ServletContext servletContext = ServletActionContext.getServletContext();
Servlet servlet = JspSupportServlet.jspSupportServlet;
velocityManager.init(servletContext);
boolean usedJspFactory = false;
PageContext pageContext = (PageContext) ActionContext.getContext().get(ServletActionContext.PAGE_CONTEXT);
if (pageContext == null && servlet != null) {
jspFactory = JspFactory.getDefaultFactory();
pageContext = jspFactory.getPageContext(servlet, request, response, null, true, 8192, true);
ActionContext.getContext().put(ServletActionContext.PAGE_CONTEXT, pageContext);
usedJspFactory = true;
}
try {
String encoding = getEncoding(finalLocation);
String contentType = getContentType(finalLocation);
if (encoding != null) {
contentType = contentType + ";charset=" + encoding;
}
Template t = getTemplate(stack, velocityManager.getVelocityEngine(), invocation, finalLocation, encoding);
Context context = createContext(velocityManager, stack, request, response, finalLocation);
StringWriter stringWriter = new StringWriter();
t.merge(context, stringWriter);
context.put(KEY_SCREEN_CONTENT, stringWriter.toString());
Object obj = context.get(KEY_LAYOUT);
String layout = (obj == null) ? null : obj.toString();
defaultLayout = (String) velocityManager.getVelocityEngine().getProperty(PROPERTY_DEFAULT_LAYOUT);
layoutDir = (String) velocityManager.getVelocityEngine().getProperty(PROPERTY_LAYOUT_DIR);
if (!layoutDir.endsWith("/")) {
layoutDir += '/';
}
if (!layoutDir.startsWith("/")) {
layoutDir = "/" + layoutDir;
}
defaultLayout = layoutDir + defaultLayout;
if (layout == null) {
layout = defaultLayout;
} else {
layout = layoutDir + layout;
}
Template layoutVm = null;
try {
inputEncoding = (String) velocityManager.getVelocityEngine().getProperty(PROPERTY_INPUT_ENCODING);
layoutVm = getTemplate(stack, velocityManager.getVelocityEngine(), invocation, layout, inputEncoding);
} catch (Exception e) {
LOG.error("VelocityLayoutResult: Can't load layout \"" + layout + "\": " + e);
if (!layout.equals(defaultLayout)) {
layoutVm = getTemplate(stack, velocityManager.getVelocityEngine(), invocation, defaultLayout,
inputEncoding);
}
}
outputEncoding = (String) velocityManager.getVelocityEngine().getProperty(PROPERTY_OUTPUT_ENCODING);
Writer writer = new OutputStreamWriter(response.getOutputStream(), outputEncoding);
response.setContentType(contentType);
layoutVm.merge(context, writer);
writer.flush();
} catch (Exception e) {
LOG.error("Unable to render Velocity Template, '" + finalLocation + "'", e);
throw e;
} finally {
if (usedJspFactory) {
jspFactory.releasePageContext(pageContext);
}
}
return;
}
}
然后在struts.xml中就可以配置了，我的配置如下：
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.velocity.toolboxlocation" value="WEB-INF/toolbox.xml" />
<constant name="struts.velocity.configfile" value="WEB-INF/velocity.properties" />
<include file="struts-default.xml" />
<package name="default" extends="struts-default">
<result-types>
<result-type name="velocity" class="struts2.velocity.VelocityLayoutResult"/>
</result-types>
<action name="hello" class="test.Hello" method="execute">
<result name="success" type="velocity">result.vm</result>
</action>
</package>
</struts>
接下来就可以开始velocity layout之旅了